New
#290
Yes, but only with builds 10565 and later. Build 10565 is an Insider build. Build 10586 is the Fall Update and there won't be an official Media Creation Tool site for it until it releases to the general public in a few days. Insiders already are on Build 10586 and many have made their own .iso files for it. I did.
With the Fall Update (or insider builds 10565 and 10576) the is a link at the bottom of the product key page (during clean installs) that says "I don't have a product key." If the user clicks the link Setup searches for OEM activation data for Windows 7 and 8 and automatically activates if it finds such data. Or the user can enter a Windows 7 or 8 key for the same edition (Home for Home, Pro for Pro) and Setup activates if the key is available. Setup does check whether or not the key is available. It detects keys that are in current use so you need to use the same key that you used to activate the version (Windows 7 or 8) on the current computer. Overloading a key (same 7 or 8 key that has been used to activate another Windows 10 installation) is detected and the key is rejected.